66 PREVENTIVE AND COMBATIVE MEASURES. 



it has been pointed out that the different species of Ustilago 

 have different powers of resistance, and must be treated 

 accordingly. It has been found from experience that when 

 trustworthy and tested steeps are in general use in any neigh- 

 bourhood, the diseases of crops caused by Ustilagineae gradually 

 disappear. This is due to the fact that the smut-fungi frequent 

 principally the cultivated cereals, while they are comparatively 

 rare on the wild grasses from which, as in the case of " rusts," 

 tln-v mi-lit make their way to the cultivated forms. 



Sterilization l>y Copper Sulphate. 



The " steep " which is in most general use is that first recom- 

 mended by Klihn l in 1858. It consists of a i per cent 

 solution of copper sulphate prepared as follows : I Ib. crushed 

 commercial sulphate of copper (blue vitriol or bluestone) is 

 dissolved in hot water and added to 22 gallons of water. The 

 seed is poured into the " steep " and allowed to stand covered 

 with the liquid for a night (twelve to sixteen hours). The 

 seed is then taken out and allowed to drip. An improvement 

 on this method consists in running off the copper sulphate 

 liquor and adding milk of lime (prepared by soaking 1 Ib. 

 good lime in 4 gallons of water), after stirring for about five 

 minutes, again run off the liquor arid allow the grain to drip. 



If sown by hand the seed may be used in a few hours, if 

 by machine it must dry for twenty-four hours. 



Sterilization by Hot Water. 



Jensen's method for treatment of seed-grain b} r hot water, 

 consists in placing the seed for a certain time in water at a 

 temperature which does not injure the grain, but is sufficient to 

 kill any adherent smut-spores. This takes place in five minutes 

 in water at 132 F. (55 C.), but the germinating .power of 

 the grain will not be injured though it remains a quarter of 

 an hour. The immersion is carried out by placing the seed in 

 a vessel easily permeable by water; a bushel basket lined with 

 coarse canvas serves very well. A convenient quantity of seed 



'Julius Kiihn, Die Krankheiten d. Kitlturgeivcichse, 1858, p. 86. Numerous 

 articles on this subject have from time to time appeared in the agricultural 

 .Journals and Bulletins. 



